The present invention relates to electric pressure switches of the type that are often used by passengers for opening railway car doors.
In order to make these switches themselves or their function upon operation visible, it is known to provide the actuating means thereof with a window-shaped transparent cover consisting of plastic, behind which an incandescent bulb (pilot light) is disposed. This type of switch having a pilot light requires a continuous supply of electricity in order that the pilot light remains lighted. Should the electricity fail or the incandescent bulb burn out, these prior art switches can no longer be seen when they are located in poorly lighted areas. In the past, attempts were made to eliminate these drawbacks by covering the area around such a switch with phosphorescent paint. This solution is unsatisfactory because it presents health hazards to both people and animals and, furthermore, the amount of radiation energy which could be stored was relatively slight.
In addition prior art electric pressure switches of the type have mechanical switch means which are subject to relatively rapid wear and can be easily damaged intentionally. Attempts have been made to eliminate this disadvantage by utilizing capacitive and inductive switch means, but these switch means are subject to many disturbing factors, such as stray fields, electric shunting influenced by weather conditions, etc.